1. Field of the Invention
The present invention relates to a pattern forming method which is used in a semiconductor process, and a method of manufacturing a semiconductor device by using the same.
2. Description of the Related Art
A coating method and a deposition method such as a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method are generally used as thin film forming methods in semiconductor manufacturing fields. The coating method is advantageous to make a finely uneven surface flat by coating a thin film material solution on a surface of a substrate and, and then drying and curing the thin film material solution. The deposition method is advantageous to form a film while maintaining an uneven surface of a substrate by growing a thin film from the surface of the substrate.
A method of forming a fine pattern by using a coating method is disclosed in:
Japanese Patent Publication No. 2004-191465 (Reference 1); and
Japanese Patent Publication No. 1998-073927 (Reference 2).
Reference 1 discloses a method of forming a fine resist removal pattern which has exceeded an exposure limit. A resist pattern is formed by coating a resist by using a coating method and developing the coated resist by using an exposure method. Also, a surfactant layer is formed on a surface of the resist pattern by coating a surfactant on the developed resist pattern. Furthermore, a mixing layer is formed on the surface of the resist pattern on which the surfactant layer is formed by coating a resist pattern thickening material on the resist pattern and then integrating the resist pattern thickening material to the resist pattern through the surfactant layer, thereby thickening the resist pattern (see Paragraph [0091] of Reference 1). A fine resist pattern which has exceeded an exposure limit is formed by removing a portion of the resist pattern thickening material which is not formed into the mixing layer.
Similarly to Reference 1, Reference 2 discloses a method of forming a fine resist pattern which has exceeded an exposure limit. A resist pattern containing an acid generating material that generates an acid by exposure is formed by coating a resist containing the acid generating material by using a coating method and developing the coated resist by using an exposure method. Also, a resist containing a cross-linking material that performs a cross-linking function due to an acid is coated on the resist pattern, acid is generated on the resist pattern by heating or exposing the resist pattern, and the resist pattern is covered with a cross-linking layer formed on an interface, thereby thickening the resist pattern. A fine resist pattern which has exceeded an exposure limit is formed by removing a portion of the resist containing the cross-linking material which is not formed into the cross-linking layer.
References 1 and 2 provide a fine resist pattern which has exceeded an exposure limit. For this, a resist pattern is required to be thickened. However, References 1 and 2 do not reduce a cost for forming a thin film or realize a high throughput.
A coating method has a lower cost and a higher throughput than a deposition method. However, differently from the deposition method, a conformal film in which an uneven surface of a substrate is maintained cannot be formed when an ordinary coating method is used. Since a material used to form a film is fluid, concavities of the substrate are filled with priority and convexities of the substrate are not covered with the film until the surface of the substrate becomes flat.